I would start out slow..... like 5 mg first day and work your way up to the prescribed dose.
I'm on 10 mg right now and am finally through the side effects (still no appetite though), just waiting for the meds to kick in a little more.
Remember, as with any prescribed medication, the manufacturer has to put every single possilbe side effect even if it does not affect the vast majority of people that take the medicaiton. There can be side effects with SSRIs like Celexa and Prozac. When I was on Zoloft, my sex drive definitely went down, however, this is not the case with everyone. Just because you experienced side effects with Prozac does not mean they will be the same with Celexa. Just remember, that there is typically an 'adjustment period' whenever you start, stop, or adjust dosages with these medications, so being patient is someitmes warranted in my opinion....although that is much easier said than done...keep us posted!